The present invention relates to a device for causing the shedding of ice from suspended cables, and particularly suspended power lines. During winter weather, or in cold climates, storms can occur that may cause an extensive build-up of ice on suspended cables and power lines. Although these storms are somewhat rare, when they do occur the potential for damage, especially to power lines, is great. Like other suspended cables, suspended power lines must support their own weight, which causes a strain on both the material of the power lines, as well as the devices used to secure the power lines to poles, towers, or other support structures. The build-up of ice on power lines can greatly increase their weight, especially on long spans, thereby also increasing the strain on the power lines and securing devices.
Past ice storms have caused significant damage to power lines in various parts of the country, resulting in disruptions in service and significant repair costs. When ice accumulation becomes sufficient to down power lines, electrical service may be disrupted to large areas, especially if the break occurs in a major, high-voltage power line. Such breaks often require difficult and time consuming repairs, both because inclement weather may make for arduous working conditions, and because high-voltage power lines often traverse remote and rugged terrain that is difficult to reach. Additionally, because such storms may effect a rather large area, an even greater number of more common, low-voltage power lines may potentially suffer damage.
Electric utilities recognize this problem and have attempted a variety of solutions. In fact, it has been determined that there are in excess of thirty different documented techniques that have been explored in regard to the icing problem. One of the most common techniques is likely thermal de-icing; whereby the power lines are heated either by increasing the current passing therethrough, or by passing current through an external jacket of resistive wires or similar material. Unfortunately, thermal de-icing has shown little success and can be an extremely costly process. Passive techniques have also been employed. These techniques may utilize special coatings to help impede the build-up of ice or lessen its ability to bond to the power lines. Passive methods have also proven generally inefficient and unreliable. A limited number of mechanical methods have also been attempted, however, to date, only rolling of the power lines has proven to be practical, albeit not overly effective.
Therefore, what is needed, but has been heretofore unavailable, is an efficient, dependable and cost effective method of preventing or reducing potentially damaging ice accumulation on power lines. The present invention satisfies this need. The present invention contemplates a relatively inexpensive, easy to install, mechanical device that takes advantage of a power line""s ability to oscillate at different frequencies when excited into motion.
The ice-shedder of the present invention may be installed on virtually any suspended cable or power line, and may be powered either by the current traveling through a power line on which the ice-shedder is installed, by a local power source, such as battery or storage capacitor, or by both. In general, the ice-shedder uses an electric motor to drive an unbalanced load, thereby producing a vibration of some frequency. When attached thereto, this vibration is transferred to the cable or power line to cause its oscillation. By varying the speed of the motor, the cable or power line may be driven through a series of frequencies that cause a shedding of the ice, or at least a significant portion thereof, that has accumulated on the power line.
The ice-shedder of the present invention may be permanently affixed to a suspended cable or power line, or may be temporarily installed. As may be desirable in permanent installations, in order to determine whether ice build-up has occurred and shedding is required, the ice-shedder can be adapted to monitor certain conditions, such as ambient temperature and the inclination of the cable or power line. If it is determined that shedding is required, the ice-shedder may automatically begin operation. In either permanent or temporary installations, the ice-shedder may be further adapted for operation by remote control or other remote starting means.